build: add jshint to scripts and ci build

.travis.yml

@@ -17,3 +17,4 @@ node_js:
 script:
   - npm run regtest
   - npm run test
+  - npm run jshint

package.json

@@ -34,6 +34,7 @@
     "verify": "./scripts/download --skip-bitcoin-download --verify-bitcoin-download",
     "test": "NODE_ENV=test mocha -R spec --recursive",
     "regtest": "./scripts/regtest",
+    "jshint": "jshint --reporter=node_modules/jshint-stylish ./lib",
     "coverage": "NODE_ENV=test istanbul cover _mocha -- --recursive"
   },
   "tags": [
@@ -67,6 +68,8 @@
     "benchmark": "1.0.0",
     "bitcore-p2p": "^1.1.0",
     "chai": "^3.5.0",
+    "jshint": "^2.9.2",
+    "jshint-stylish": "^2.1.0",
     "mocha": "^2.4.5",
     "proxyquire": "^1.3.1",
     "rimraf": "^2.4.2",